Tensioner device

ABSTRACT

A tensioner device  14  for an engine  1  comprises a support member  16 , a blade shoe  17  coming into sliding contact with a timing chain  11  having a base end section  17   a  held by a cylinder block  3  and a tip end section  17   b  supported by the support member  16 , and a leaf spring  18  held by the blade shoe  1  for pressing the blade shoe  17  against the timing chain  11  elastically. The support member  16  is formed integrally with the cylinder block  3 . The tip end section  17   b  comes into sliding contact with a guide surface  16   a  formed on the support member  16  to be supported.

TECHNICAL FIELD

The present invention relates to a tensioner device of an transmissionendless flexible member such as a chain and a belt used for transmittingpower of a driving shaft of an engine to auxiliary machinery such as avalve moving apparatus or an oil pump to drive it.

BACKGROUND ART

Hitherto, a transmission endless flexible member such as a chain or abelt for transmitting power from a drive shaft of an engine has atensioner device for adjusting tension of the endless flexible memberautomatically, in order to give a proper tension for transmitting powersmoothly and in order to prevent vibration of the endless flexiblemember caused by change of tension of the endless flexible member owingto change of rotation of the driving shaft.

For example, in a chain tension adjusting apparatus disclosed inJapanese Laid-Open Patent Publication Sho 61-48655, a tension givingmember consisting of a plate spring and a plastic plate joined togetheris brought into contact with a loose side of a chain wound roundsprockets attached to a crankshaft and a valve driving cam shaftrespectively. The tension giving member has a lower end pivoted to acrankcase and an upper end pivoted to a piston member of a tensionadjusting mechanism. The piston member is fitted to a guide hole of acase formed on a cylinder head so as to slide, and forced by a coilspring held by a screw member so as to bent the tension giving membertoward the chain for giving tension to the chain.

In the prior art disclosed in the above-mentioned publication, the upperend of the tension giving member for pressing the chain to give tensionis supported by the piston member which is movable only in a directionto increase the tension of the chain, because loosing of the chain mustbe compensated.

Therefore, the above-mentioned tension adjusting mechanism is separatedfrom the engine main body such as a cylinder head and the like, and thecoil spring forcing the piston member and the screw member holding thecoil spring are necessary, so that the construction for supporting theupper end of the tension giving member requires a large number of partsand is complicated.

DISCLOSURE OF INVENTION

The present invention has been accomplished in view of the foregoing,and an object of the inventions is to provide a tensioner device havinga small number of parts and a simple construction. Another object of theinvention is to improve rigidity of a support member on which a forceacts from a tensioner shoe, a further object of the inventions is toprevent falling of the tension shoe in the width direction thereof, andthe other object of the invention is to lubricate a sliding part forimproving durability of the tensioner device.

The present invention provides a tensioner device including a supportmember provided on an engine main body, a tensioner shoe coming intosliding contact with a transmission endless flexible member having abase end section held by the engine main body and a tip end sectionsupported by the support member so as to slide, and a spring pressingthe tensioner shoe against the endless flexible member elastically,wherein the support member is formed integrally with the engine mainbody, and the tip end section is supported touching a guide surfaceformed on the support member so as to slide.

According to the invention, the support member supporting the tip endsection of the tensioner shoe is formed integrally with the engine mainbody to reduce the number of parts, and the support member can be formedconcurrently with the engine main body to reduce the cost. The supportmember is formed with only a guide surface coming into sliding contactwith the tip end section and has no moving portion, so that theconstruction is simplified and the durability is improved.

Since the guide surface is formed on the support member which is formedintegrally with the engine main body, there is no attachment errorbetween the engine main body and the support member and positionalrelation between the guide surface and the tensioner shoe is setaccurately, so that a tensioner device with good tension adjustingfunction having no substantial deflection for every engine can beobtained.

The tip end section can be set on the guide surface concurrently withattachment of the tensioner shoe to the engine main body, so that thetensioner device can be installed in the engine easily.

In the above-mentioned tensioner device, the support member may have areinforcement section provided substantially along line of force actingon the guide surface of the support member from the tip end section.

Since force acting on the support member from the tip end section isreceived by the reinforcement section, rigidity of the support membercan be raised to effect a stable tension adjusting function. Further,since the reinforcement section supports the majority of the forceacting on the support member from the tip end section, a part of thesupport member hardly contributing to raise the rigidity can be madethin to make the engine light.

In the above-mentioned tensioner device, a projection for regulatingdisplacement of the tensioner shoe in a width direction thereof bytouching the tip end section may be provided on at least one of memberspositioned on both sides of the tip end section in the width direction.

The displacement of the tensioner shoe in the width direction, which iscaused by movement of the endless flexible member since the tip endsection slides on the guide surface, can be made minute by the tip endsection touching the projection of the member positioned on a side ofthe tip end section in the width direction. Therefore, it is possible toprevent falling down of the tensioner shoe, and a stable tensionerfunction can be exhibited. Further, since the projection can be formedutilizing a member positioned in the neighborhood of the tip endsection, for example a case covering the endless flexible member, or theengine main body, the falling down of the tensioner shoe can beprevented without increasing the number of parts. When the tensionershoe with the base end section held by the engine main body isdisplaced, displacement is largest at the tip end section. According tothis invention, displacement of the tensioner shoe is regulated at thetip end section, therefore displacement of the entire tensioner shoe canbe made minute easily.

In the above-mentioned tensioner device, a projection for regulatingdisplacement of the tensioner shoe in a width direction thereof bytouching a member opposite to a side face of the tip end section may beprovided on at least one of both sides of the tip end section in thewidth direction.

The displacement of the tensioner shoe, which is caused by movement ofthe endless flexible member since the tip end section slides on theguide surface, can be made minute by the projection on a side of the tipend section in the width direction touching the member opposite to theside of the tip end section. Therefore, it is possible to preventfalling down of the tensioner shoe, and a stable tensioner function canbe exhibited. Further, since the projection is formed at the tip endsection, the falling down of the tensioner shoe can be prevented easilyeven if the tip end section is in any position. When the tensioner shoewith the base end section held by the engine main body is displaced,displacement is largest at the tip end section. According to thisinvention, displacement of the tensioner shoe is regulated at the tipend section, therefore displacement of the entire tensioner shoe can bemade minute easily.

Further, in the above-nebtioned tensioner device, the guide surface mayhave an upper guide surface portion extending upward from a touchingposition of the guide surface and the tip end section, a surface of thetip end section opposite to the guide surface may have an upper oppositesurface portion extending upward from the touching position, and theupper guide surface portion and the upper opposite surface portion mayform a space widened toward above to guide lubricating oil flowing ontothe upper guide surface portion and the upper opposite surface portionto the touching position.

Lubricating oil flowing down from the above is caught in the widenedspace, and supplied to the touching section along the upper guidesurface portion and the upper opposite surface portion for lubricatingthe touching position, so that abrasion of the support member and thetip end section can be reduced. As the result, durability of the supportmember and the tip end section can be improved, and a proper tensionadjusting is possible over a long period of time.

In this description, the engine main body means at least one memberamong a cylinder block, a cylinder head, a crankcase, a cover to beattached to any one f the above members and a housing for an instrumentto be driven by the engine which is integral with the cylinder block,the cylinder head, the crankcase or the cover by fixing or forming.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a side view of an essential part of an engine from which achain case is removed, showing a first embodiment in which the presentinvention is applied to a cam chain;

FIG. 2 is a sectional view taken along the line II—II of FIG. 2;

FIG. 3 is a side view of an essential part of an engine according to asecond embodiment in which the present invention is applied to a chainfor driving a oil pump; and

FIG. 4 is a sectional view taken along the line IV—IV of FIG. 3.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, some embodiments of the present invention will be describedwith reference to FIGS. 1 to 4. FIGS. 1 and 2 show the first embodiment.FIG. 1 is a side view of an engine from which a chain case is removed,and FIG. 2 is a sectional view taken along the line II—II of FIG. 1.

In the first embodiment, an engine 1 which is an overhead camshaft typeinternal combustion engine has a lower block (a lower crankcase) 2attached with an oil pan (not shown) below, a cylinder block (a cylinderand an upper crankshaft) 3, a cylinder head 4 and a cylinder head cover(not shown), assembled being piled up in turn.

A camshaft 7 supported on the cylinder head 4 so as to rotate is drivenat a rotational speed corresponding to ½ of a rotational speed of acrankshaft 5 by a timing chain (a transmission endless flexible member)11 wound round a drive sprocket 6 attached to the crank shaft 5, a camsprocket 8 attached to the camshaft 7 and a pump sprocket 10 attached toa rotary shaft 9 of an oil pump. The crankshaft 5 is a drive shaft, andthe camshaft 5 and the rotary shaft 9 are driven shafts. The timingchain is covered by a chain case 12 (FIG. 2) which is fixed by bolts oncontact surfaces 2 a, 3 a, 4 a formed on the lower block 2, the cylinderblock 3 and the cylinder head 4.

The timing chain 11 is given a proper tension automatically by a chainguide 13 coming into contact with the timing chain 11 at a tensile sidebetween the cam sprocket 8 and the pump sprocket 10, and a tensionerdevice 14 having a blade shoe (tensioner shoe) 17 coming into contactwith the timing chain 11 at a loosened side between the drive sprocket 6and the cam sprocket 8.

The tensioner device 14 is composed of a tensioner main body 15 and asupport member 16. The tensioner main body 15 is composed of a bladeshoe 17 made of plastics, nylon for example, and a leaf spring 18 formedby a plurality of layers of plate springs, five layers in thisembodiment, coming into contact with a back surface of the blade shoe 17to press the blade shoe 17 against the timing chain 11 elastically. Theleaf spring 18 is held to the blade shoe 17 at the both ends 18 a, 18 binserted in grooves 17 c, 17 d formed at a base end section 17 a and atip end section 17 b of the blade shoe 17, respectively. The platesprings are not necessarily fixed to each other, and may be merely piledup being separated from each other.

The blade shoe 17 has an arcuate side view and a predetermined width ina direction parallel with the axis of the crankshaft 5. The base endsection 17 a of the blade shoe 17 is pivotally supported by a supportshaft 19 which is fixed to the cylinder block 3 at the neighborhood ofthe drive sprocket 6 attached to the crankshaft 5. The crankshaft 5 isdisposed between the lower block 2 corresponding to a lower crankcaseand a lower portion of the cylinder block 3 corresponding to an uppercrankcase.

The tip end section 17 b of the blade shoe 17 is positioned in aneighborhood of a contact surface between the cylinder block 3 and thecylinder head 4 striding the contact surface and supported by a guidesurface 16 a of the support member 16 which comes into sliding contactwith the tip end section 17 b. The tensioner main body 15 is pressedagainst the timing chain 11 by the guide surface 16 a touching the tipend section 17 b so that the blade shoe 17 comes into sliding contactwith the timing chain 11. The timing chain 11 is given a proper tensionby elastic force of the leaf spring 18.

The guide surface 16 a is formed in a plane inclining obliquely downwardtoward the timing chain 11, so that when the timing chain 11 isloosened, the tensioner main body 15 is moved to press the timing chain11 more. Degree of pressing given to the timing chain 11 by elasticforce of the leaf spring 18 can be adjusted by degree of the inclinationof the guide surface 16 a.

Namely, when the timing chain 11 is loosened, the tip end sectionpinched between the guide surface 16 a and the timing chain 11 slides onthe guide surface 16 a in a direction to press the timing chain 11,because curvature of the tensioner main body is increased by elasticforce of the leaf spring 18. On the one hand, when the timing chain 11is tensed, the tip end section 17 b slides on the guide surface 16 a ina direction contrary to the above.

The tip end section 17 b positioned between the groove 17 d holding theleaf spring 18 and the support member 16 is formed with a hollow 17 e tolighten the tip end section 17 b. Further, the tip end section 17 b isformed with a reinforcement rib 17 f extending substantially in adirection of line of reaction force from the support member 16 to givethe tip end section 17 b rigidity against the reaction force.

The support member 16 is positioned at a part of the cylinder block 3near the cylinder head 4 and swells toward the inner side from a rearend wall 3 b of the cylinder block 3. A hollow 16 b is formed in thesupport member 16 so that the support member 16 is made as a swellingportion having a thin wall. The support member 16 is formed togetherwith the cylinder block 3 when the cylinder block is cast.

The support member 16 has a reinforcement rib 16 c in addition to theabove-mentioned guide surface 16 a on which the tip end section 17 b ofthe blade shoe 17 slides in accordance with fluctuation of tension ofthe timing chain 11. The rib 16 c extends substantially along line offorce acting on the support member 16 from the tip end section 17 b at atouching position of the guide surface 16 a and the tip end section 17b. The rib 16 c is formed so as to extend from an inner surface of thesupport member 16 opposite with the guide surface 16 a to a thick bosssection 22 of the rear end wall 3 b of the cylinder block 3. The bosssection 22 is formed with a tapped hole 21 engaging with a bolt 20 forattachment of the chain case 12 (FIG. 2).

The guide surface 16 a has an upper guide surface portion 16 d extendingupward from the touching position of the guide surface 16 a and the tipend section 17 b within a predetermined extent. The curved surface 17 gof the tip end section 17 b opposite to the guide surface 16 a has anupper opposite surface portion 17 h extending upward from the touchingposition within a predetermined extent. The upper guide surface portion16 d and the upper opposite surface portion 17 h form a wedge-shapedspace 23 widened toward above to guide lubricating oil flowing onto theupper guide surface portion 16 d and the upper opposite surface portion17 h to the touching position. The above-mentioned predetermined extentis set properly corresponding to shapes of the guide surface 16 a andthe opposite surface 17 g in view of necessary supply of lubricating oilto the touching position.

A part of lubricating oil supplied for lubricating the timing chain 11and the cam sprocket 8 positioned above the space 23, the drive sprocket6 and the pump sprocket 10 drops to be caught in the space 23. Thecaught lubricating oil is supplied to the touching position directly oralong the upper guide surface portion 16 d and the upper oppositesurface portion 17 h.

As shown in FIG. 2, in a width direction A of the blade shoe 17, on aside face of the tip end section 17 b near the cylinder block 3 isformed a long and slender projection 17 k opposite to the cylinder block3 and the cylinder head 4 (see FIG. 1, too). The gap between the tip endsection 17 b and the cylinder block 3 and the cylinder head 4 is mademinute by the projection 17 k and displacement of the tensioner mainbody 15 toward the cylinder block 3 and the cylinder head 4 is regulatedto be minute. The gap between a portion of the tip end section 17 b notformed with the projection 17 k and the cylinder block 3 and thecylinder head 4 is set to an extent that the leaf spring 18 does notescape from the groove 17 d in the width direction A.

The chain case 12 has a long and slender projection 12 a projectinginside at a region in which the tip end section 17 b moves sliding onthe guide surface 16 a in accordance with fluctuation of tension of thetiming chain 11 (see FIG. 1, too). The gap between the tip end section17 b and the chain case 12 is made minute by the projection 12 a, sothat displacement of the tensioner main body 15 toward the chain case 12is regulated to be minute. Movement of the leaf spring 18 from thegroove 17 d toward the chain case 12 is restrained by the projection 12a to prevent escape of the leaf spring 18.

The projections 17 k, 12 a extend so as to intersect each other in theside view as shown in FIG. 1, so that movement of the tensioner mainbody 15 in the width direction owing to change of tension of the timingchain is restrained small.

In the above-mentioned first embodiment, since the support member 16supporting the tip end section 17 b of the blade shoe 17 is formedintegrally with the cylinder block 3 that is an engine main body, thenumber of parts is reduced and the cost can be reduced because thesupport member 16 can be formed concurrently with the cylinder block 3.Since the support member 16 is formed with only the guide surface 16 afor coming into sliding contact with the tip end section 17 b and nomovable section, the construction is simple and the durability isimproved.

Since the guide surface 16 a is formed on the support member 16 which isformed integrally with the cylinder block 3, there is no attachmenterror between the cylinder block 3 and the support member 16 andpositional relation between the guide surface 16 a and the tip endsection 17 b of the blade shoe 17 is set accurately, so that a tensionerdevice 14 with good tension adjusting function having no substantialdeflection at every engine can be obtained.

The tip end section 17 b can be set on the guide surface 16 aconcurrently with attachment of the leaf blade 17 holding the leafspring 18 to the cylinder block 3, so that the tension device 14 can beinstalled in the engine 1 easily.

Since the base end section 17 a of the blade shoe 17 is held by thecylinder block 3 and the support member 16 for supporting the tip endsection 17 b is also formed on the same cylinder block 3, assemblingaccuracy is improved.

Since force acting on the support member 16 from the tip end section 17b is received by the rib 16 c, rigidity of the support member 16 can beraised to effect a stable tension adjusting function. Further, since therib 16 c supports the majority of the force acting on the support member16 from the tip end section 17 b, a part of the support member 16 hardlycontributing to raise the rigidity can be made in a thin constructionwith the hollow 16 b to make the engine 1 light. In addition, the rib 16c extends up to the boss section 22 of the cylinder block 3 which ismade thick for forming the tapped hole 21 engaging with the bolt 20, sothat a large force can be received sufficiently.

Since the tip end section 17 b formed with the hollow 17 e is light inweight, the tensioner main body 15 follows movement of the timing chain11 owing to fluctuation of tension well. The tip end section 17 b has ahigh rigidity in spite of its light weight, because the tip end section17 b has the rib 17 f formed in a direction substantially along line ofreaction force from the support member 16 to give rigidity forencountering the reaction force.

Displacement of the tensioner main body 15 toward the chain case 12 inthe width direction A can be made minute by the long and slenderprojection 12 a of the chain case 12 touching the tip end section 17 b,therefore falling down of the tensioner main body 15 can be preventedand stable tensioner function can be effected. Since the projection 12 acan be formed utilizing the chain case 12 positioned near the tip endsection 17 b, falling down of the tensioner main body 15 can beprevented without increasing the number of parts. Since the displacementis regulated at the tip end section 17 b where the largest displacementoccurs when the cylinder block 3 having the base end section 17 a heldto the cylinder block 3 is displaced, displacement of the entiretensioner main body 15 can be made minute easily.

Displacement of the tensioner main body 15 toward the cylinder block 3and the cylinder head 4 can be made minute by the projection 17 k of thetip end section 17 b touching at least one of the cylinder block 3 andthe cylinder head 4, therefore falling down of the tensioner main body15 can be prevented and stable tensioner function can be effected. Sincethe projection 17 k is formed on the tip end section 16 b, the tip endsection 16 b can be brought into contact with at least one of thecylinder block 3 and the cylinder head 4 at every position so thatfalling down of the tensioner main body 15 can be prevented easily.

Since the projections 17 k, 12 a extend so as to intersect each other inthe side view as shown in FIG. 1 so that movement of the tensioner mainbody 15 in the width direction owing to change of tension of the timingchain is restrained small, falling down of the tensioner main body 15can be prevented surely at every position of the tip end section 17 b.

Some of lubricating oil for lubricating the timing chain 11 and thesprockets 6, 8, 10 drops from the above and is caught in the space 23,then the caught lubricating oil is supplied to the touching position ofthe guide surface 16 a and the tip end section 17 b along the upperguide surface portion 16 a and the upper opposite surface portion 17 h.Therefore, abrasion of the guide surface 16 a and the tip end section 17b can be reduced to improve durability of the support member 16 and thetip end section 17 b and proper tension adjusting is possible over along period of time.

Next, the second embodiment will be described with reference to FIGS. 3and 4. FIG. 3 is a side view of an essential part of an engine, and FIG.4 is a sectional view taken along the line IV—IV of FIG. 3.

As shown in FIG. 3, in the engine which is an internal combustionengine, a chain (transmission endless flexible member) 36 is wound rounda drive sprocket 32 attached to a crankshaft 31 of the engine and adriven sprocket 35 attached to a rotary shaft 34 of a trochoid-type oilpump 33, for driving the oil pump 33. A pump housing 37 for housing arotor of the oil pump 33 is fixed to a lower block by bolts. Thecrankshaft 31 is a drive shaft and the rotary shaft 34 is a drivenshaft.

The chain 36 is given proper tension automatically by a chain guide 38coming into sliding contact with the tensile side of the chain 36 and atensioner device 40 having a blade shoe (tensioner shoe) 43 coming intosliding contact with the loosened side of the chain 36. The chain guide38 is fixed to the lower block by bolts 39.

The tensioner device 40 is composed of a tensioner main body 41 and asupport member 42. The tensioner main body 41 is composed of a bladeshoe 43 made of plastics, nylon for example, and a leaf spring 18 formedby a plurality of layers of plate springs, two layers in thisembodiment, coming into contact with a back surface of the blade shoe 43to press the blade shoe 43 against the chain 36 elastically. The leafspring 44 is held to the blade shoe 43 at both ends 44 a, 44 b insertedin grooves 43 c, 43 d formed at a base end section 43 a and a tip endsection 43 b of the blade shoe 43 leaving thin walls on a side opposingto the pump housing 43, respectively. The plate springs are fixed toeach other, or piled up being separated from each other.

The arcuate blade shoe 43 has a predetermined width in a directionparallel with the axis of the crankshaft 31. The base end section 43 ais pivoted on a support shaft 45 fixed to the lower block. The tip endsection 43 b is supported by a guide surface 42 a formed on the supportmember 43 which the tip end section 43 b touches so as to slide.Therefore, the tensioner main body 41 is pressed by the chain 36 and theblade shoe 43 comes into sliding contact with the chain 36. At thattime, the chain 36 is given proper tension by elastic force of the leafspring 44.

The guide surface 42 a is formed in a plane inclining obliquely upwardtoward the chain 36, so that when the chain 36 is loosened, thetensioner main body 41 is moved further in a direction to press thechain 36. In the second embodiment, since the distance between thecrankshaft 31 and the rotary shaft of the oil pump 33 is short, thechain 36 is shorter than the timing chain 11 of the first embodiment andthe tension fluctuation is also smaller. Therefore, inclination of theguide surface 42 a is made relatively large so that the tensioner mainbody 41 can be moved corresponding to the tension fluctuation.

When the chain 36 is loosened, the tip end section 43 b pinched betweenthe guide surface 42 a and the chain 36 slides on the guide surface 42 ain a direction to press the chain 36, because curvature of the tensionermain body 41 is increased by elastic force of the leaf spring 44. On theone hand, when the chain 39 is tensed, the tip end section 43 b slideson the guide surface 42 a in a direction contrary to the above.

The support member 42 is formed as a flat wall projecting from an outersurface of the pump housing 37 in an axial direction of the crankshaft31. The support member 42 is formed together with the pump housing 37integrally when the pump housing 37 is cast.

The support member 42 has a reinforcement rib 42 b in addition to theabove-mentioned guide surface 42 a on which the tip end section 43 b ofthe blade shoe 43 slides in accordance with fluctuation of tension ofthe chain 36. The rib 42 b is formed on a back surface of the supportmember 42 and extends substantially along a line of force acting on thesupport member 42 from the tip end section 43 b at a touching positionof the guide surface 42 a and the tip end section 43 b.

The guide surface 42 a has an upper guide surface portion 42 c extendingupward from the touching position of the guide surface 42 a and the tipend section 43 b within a predetermined extent. The curved surface 43 eof the tip end section 43 b opposite to the guide surface 42 a has anupper opposite surface portion 43 f extending upward from the touchingposition within a predetermined extent. The upper guide surface portion42 c and the upper opposite surface portion 43 f form a wedge-shapedspace 46 widened toward above to guide lubricating oil flowing onto theupper guide surface portion 42 c and the upper opposite surface portion43 f to the touching position. The above-mentioned predetermined extentis set properly corresponding to shapes of the guide surface 42 a andthe opposite surface 43 e in view of necessary supply of lubricating oilto the touching position.

A part of lubricating oil supplied to the chain 36 and the drivesprocket 32 positioned above the space 46 and a part of lubricating oilsupplied to the driven sprocket 35 and having lubricated the sprocket 35drop in the space 46 to be caught. The caught lubricating oil issupplied to the touching position directly or along the upper guidesurface portion 42 c and the upper opposite surface portion 43 f.

As shown in FIG. 4, the oil pan 47 has a long and slender projection 47a projecting inside at a region in which the tip end section 43 b movessliding on the guide surface 42 a in accordance with fluctuation oftension of the chain 36 (see FIG. 3, too). The gap between the tip endsection 43 b and the oil pan 47 is made minute by the projection 47 a,so that displacement of the tensioner main body 15 toward the oil pan 47is regulated to be minute. Movement of the leaf spring 44 from thegroove 43 d toward the oil pan 47 is restrained by the projection 47 ato prevent escape of the leaf spring 44.

The pump housing 37 positioned on another side in width direction B ofthe blade shoe 43 is opposite to the tip end section 43 b through aminute gap to regulate movement of the tip end section 43 b toward thepump housing 37.

In the second embodiment, since the distance between the crankshaft 31and the rotary shaft 34 of the oil pump 33 is short and correspondinglylength of the tensioner main body 41 is short, extent of movement of thetip end section 43 b owing to tension fluctuation of the chain 36 isrelatively narrow. Therefore, only one projection 47 a is provided.

Next, effect of the second embodiment constituted as mentioned abovewill be described. Since the support member 42 supporting the tip endsection 43 b of the blade shoe 43 is formed integrally with the pumphousing 37 namely an engine main body, the number of parts can bereduced. In addition, since the support member 42 can be formedconcurrently with the pump housing 37, cost reduction is possible. Thesupport member 42 has only the guide surface 42 a which the tip endsection 43 b comes into sliding contact with, and no movable part.Therefore, the construction is simple and durability is improved.

Since the guide surface 42 a is formed on the support member 42 which isformed integrally with the pump housing 37, there is no attachment errorbetween the pump housing 37 and the support member 42 and positionalrelation between the guide surface 42 a and the tip end section 43 b ofthe blade shoe 43 is set accurately, so that a tensioner device 40 withgood tension adjusting function having no substantial deflection atevery engine can be obtained.

The tip end section 43 b can be set on the guide surface 42 aconcurrently with attachment of the blade shoe 43 holding the leafspring 44 to the lower block, so that the tensioner device 40 can beinstalled in the engine easily.

Force acting on the support member 42 from the tip end section 43 b isreceived by the rib 42 b, so that rigidity of the support member can beraised and stable tension adjusting function is effected.

Displacement of the tensioner main body 41 toward the oil pan 47 in thewidth direction B can be made minute by the long and slender projection47 a of the oil pan 47 touching the tip end section 43 b, therefore,falling down of the tensioner main body 41 can be prevented and stabletensioner function can be effected. Since the projection 47 a can beformed utilizing the oil pan 47 positioned near the tip end section 43b, falling down of the tensioner main body 41 can be prevented withoutincreasing the number of parts. When the tensioner main body 41 havingthe base end section 43 a held by the lower block is displaced, thelargest displacement occurs at the tip end section 43 b. Since thedisplacement is regulated at the tip end section 43 b where the largestdisplacement occurs, displacement of the entire tensioner main body 41can be made minute easily.

A part of lubricating oil for lubricating the chain 36 and the sprockets32, 35 drops from the above and is caught in the space 46, then thecaught lubricating oil is supplied to the touching position of the guidesurface 42 a and the tip end section 43 b along the upper guide surfaceportion 42 c and the upper opposite surface portion 43 f. Therefore,abrasion of the guide surface 42 a and the tip end section 43 b can bereduced to improve durability of the support member and the tip endsection 43 b and proper tension adjusting is possible over a long periodof time.

In the first embodiment, the projection for regulating displacement ofthe tensioner main body may be provided on a side face of the tip endsection 17 b near the chain case 12 in width direction A, or on at leastone of the both side faces of the tip end section 17 b in the widthdirection A. Or, the projection may be provided on the cylinder block 3and the cylinder head facing a side of the tip end section 17 b in thewidth direction A. The projection may be provided on the chain case 12.

In the second embodiment, the projection for regulating displacement ofthe tensioner main body may be provided on the pump housing 37 which isfaces with a side of the tip end section 43 b in the width direction B.The projection may be provided on at least one of the oil pan 47 and thepump housing 37. Further, the projection may be provided on the tip endsection 43 b in a similar manner to the first embodiment.

In the both embodiments, the projections 12 a, 17 k and 47 a are formedintegrally with the chain case 12, the tip end section 17 b of the bladeshoe 17 and the oil pan 47, respectively. But the projections 12 a, 17 kand 47 a may be formed with respective members separated from the chaincase 12, the tip end section 17 b and the oil pan 47.

In the both embodiments, the base end sections 17 a, 43 a of the bladeshoes 17, 43 are held to the support shafts 19, 45 so as to rotate. Butthe base end sections 17 a, 34 a may be fixedly held to the engine mainbody such as the cylinder block 3 or the pump housing 37. The base endsections 17 a, 43 a may be held to engine main bodies other than thecylinder block 3 and the lower block. The support members 16, 42 may beformed integrally with engine main bodies other than the cylinder block3 and the pump housing 37.

In the both embodiments, the tensioner devices 14, 40 are applied to thetiming chain 11 for driving the camshaft 7 and the chain 36 for drivingthe rotary shaft 31 of the oil pump 33, respectively. But the tensionerdevice may be applied to a chain for driving a balancer shaft. A beltmay be used as the transmission endless flexible member in place of thechain.

Industrial Applicability

The present invention is applicable to an engine for adjusting tensionof a transmission endless flexible member.

What is claimed is:
 1. A tensioner device, comprising: a support memberintegrally formed on an engine main body, said support member protrudingfrom the engine main body and providing a guide surface; a tensionershoe that makes sliding contact with an endless flexible transmissionmember, said tensioner shoe having: a base end section pivotallysupported by a shaft fixed to said engine main body, and a tip endsection supported by and slidably contacting the guide surface of saidsupport member for guided movement to displace the tensioner shoerelative to said endless flexible transmission member; a spring thatelastically biases said tensioner shoe against said endless flexibletransmission member; and a case provided on said engine main body andcovering said support member, said tensioner and said endless flexibletransmission member, wherein said case has a projection formed thereonand projecting inward to be adjacent said tip end section and whereinsaid case projection guides said tip end section in a direction whereinsaid tip end section is displaced for guided movement by said guidesurface.
 2. A tensioner device as claimed in claim 1, wherein saidsupport member has a reinforcement section provided substantially alonga line of force acting on said guide surface of said support member fromsaid tip end section.
 3. A tensioner device as claimed in claim 1 or 2,wherein a projection for regulating displacement of said tensioner shoein a width direction thereof by touching said tip end section isprovided on at least one of said tip end section and a chain casecovering said endless flexible transmission member positioned on eitherside of said tip end section in said width direction.
 4. A tensiondevice claimed in claim 1 or 2, wherein a projection for regulatingdisplacement of said tensioner shoe in a width direction thereof bytouching a member opposite to a side face of said tip end section isprovided on at least one of both sides of said tip end section in saidwidth direction.
 5. A tensioner device as claimed in claim 1 or 2,wherein said guide surface has an upper guide surface portion extendingupward from a touching position of said guide surface and said tip endsection, a surface of said tip end section opposite to said guidesurface has an upper opposite surface portion extending upward from saidtouching position, and said upper guide surface portion and said upperopposite surface portion form a space widened toward above to guidelubricating oil flowing onto said upper guide surface portion and saidupper opposite surface portion to said touching position.
 6. A tensionerdevice according to claim 1, wherein said projection has an elongatedshape and extends in said direction in which said tip end section isdisplaced for guided movement.
 7. A tensioner device according to claim1, further comprising a projection formed on a surface of said tip endsection, remote from said projection on said case, said projection onsaid surface of said tip end section being positioned adjacent to anouter surface of said engine main body.
 8. A tensioner device accordingto claim 7, wherein said projection on said case is elongated andextends in said direction in which said tip end section is displaced forthe guided movement, and said projection on said surface of said tip endsection is elongated and extends in a direction intersecting saidprojection on said case.
 9. A tensioner device according to claim 7,wherein said support member protrudes from said engine main body.
 10. Atensioner device according to claim 1, wherein said tip end sectioncomprises a hollow space therein.
 11. A tensioner device comprising: asupport member integrally formed on an engine main body, said supportmember protruding from the engine main body and providing a guidesurface; a tensioner shoe that makes sliding contact with an endlessflexible transmission member, said tensioner shoe having: a base endsection pivotally supported by a shaft fixed to said engine main body,and a tip end section supported by and slidably contacting the guidesurface of said support member for guided movement to displace thetensioner shoe relative to said endless flexible transmission member; aspring that elastically biases said tensioner shoe against said endlessflexible transmission member; and an oil pan provided adjacent said pumphousing and having a projection formed on said oil pan and projectinginward to be adjacent to said tip ends section and guiding said tip endsection in a direction in which said tip end section is displaced forguided movement by said guide surface.
 12. A tensioner device accordingto claim 11, wherein said projection has an elongated shape and extendsin said direction in which said tip end section is displaced for theguided movement.
 13. A tensioner device according to claim 11, whereinsaid support member protrudes from said pump housing.
 14. A tensionerdevice according to claim 11, wherein said guide surface is a flatsurface.